I’m applying RD to Columbia College, and although I haven’t won any national awards for creative writing, I have a substantial amount of work I could pull from to make a portfolio. I got a regional honorable mention from Scholastic Art and Writing Awards and published 3 novels. Most of my application seemed focused on writing/language arts. Would it add to my application if I submitted a portfolio?
It couldn’t hurt to submit a portfolio. At worst, they will just not read it. IDK whether they’d be impressed with recognition from the awards program at the honorable mention level. But again, it can’t hurt to include.
I suggest you include documentation of the publication of your novels, whether self-published or not. Best would be facsimile of an Amazon author listing showing they had some sales. If I were an adcom, that would impress me, especially if you had a well-known commercial publisher (not vanity press or self-published).
Finally, I suggest you avoid the term “creative writing.” At schools like Columbia, it tends to make people gag. Say “literary fiction” or “commercial fiction.”
Submitting a portfolio is definitely not something to be taken lightly, because though it can help you it may also hurt you if the portfolio’s quality doesn’t set you apart from other candidates (thus weakening aspects of your application related to that creative skill). If you are confident that your writing is an essential part of your application that would help ad coms better understand your passion/skill (beyond what they get from seeing listed awards or publications), then go for it.
I’m a musician and I decided to submit audition tapes to all schools that accepted them. My post-acceptance letters from several schools, including Columbia, specifically mentioned aspects of my audition tapes as positive aspects of my application! So they will indeed read your portfolio 
Also, I think saying “creative writing” should be OK! People on the Columbia Review (one of the school’s literary magazines) say “creative writing”, and so do the creative writing majors. As you probably know already, our creative writing MFA is supposed to be dope and CU has a lot of people who love writing in general.
Thank you guys so much for the advice! I was worried that adding too much writing might water down my application, but I’ll submit a sample or two of work and proceed carefully